1. Field of the Invention
The present invention relates to a semiconductor device. Note that in this specification, a semiconductor device refers to a semiconductor element itself or any device including a semiconductor element. As such a semiconductor element, a gate-insulated field-effect transistor can be given, for example. A semiconductor device also includes, in its category, a semiconductor circuit including a semiconductor element, an electro-optical device such as a display device, and an electronic device.
2. Description of the Related Art
A parity bit is a redundant bit signal which is added to a multi-bit digital data signal (hereinafter also referred to as a data potential signal) when the digital data signal is transmitted (or transferred).
Such a redundant bit is also added to a data potential signal after transmission, and parity bits before and after transmission are determined; thus, an error of a data potential signal can be determined. This determination method is called “parity check” and is generally used as a method for determining an error in data communication because determination can be performed only with a 1-bit parity bit added and because a parity bit can be generated by a plurality of XOR gates.
In recent years, metal oxides having semiconductor characteristics (hereinafter, referred to as oxide semiconductors) have attracted attention. Oxide semiconductors can be applied to transistors (see Patent Documents 1 and 2).